renal agenesis

Fraser Syndrome 2

Clinical Characteristics
Ocular Features: 

Cryptophthalmos, both unilateral and bilateral, is the ocular hallmark.  The lid margins may be fused.

Systemic Features: 

Multiple systemic malformations are usually present.  A small mouth, nasal dysplasia with hypoplastic alae nasi, and syndactyly may be seen.  Urogenital malformations such as renal dysgenesis or dysplasia, ambiguous genitalia, streak ovaries may be present.  Pulmonary hypoplasia and imperforate anus have been reported.

Genetics

Homozygous mutations in the FREM2 gene (13q13.3) have been identified in Fraser syndrome 2.  

See Fraser syndrome 1 (219000) for additional features that may be present in Fraser syndrome.

Fraser syndrome 3 (617667) results from homozygous mutations in GRIP1.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Fraser Syndrome 3

Clinical Characteristics
Ocular Features: 

Cryptophthalmos is always present.  The anterior chamber was described as 'abnormal' in several stillborn male fetuses.

Systemic Features: 

Low-set simple ears were noted in two stillborn fetuses.  Micrognathia and a broad and beaked nose with notched alae nasi were described together with a malformed and atretic larynx.  The fingers and toes may be short and cutaneous syndactyly may be present.  The position of the anus may be abnormal.  The lungs may have abnormal lobulation and appear hyperplastic and hyperechogenic.  The bladder and kidneys may be absent.

Genetics

Homozygous mutations in the GRIP1 gene (12q14.3) have been identified in this autosomal recessive condition.

Fraser syndrome 1 (219000) results from homozygous mutations in the FRAS1 gene.

Fraser syndrome 2 (617666) is caused by homozygous mutations in the FREM2 gene.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Mutations in GRIP1 cause Fraser syndrome

Vogel MJ, van Zon P, Brueton L, Gijzen M, van Tuil MC, Cox P, Schanze D, Kariminejad A, Ghaderi-Sohi S, Blair E, Zenker M, Scambler PJ, Ploos van Amstel HK, van Haelst MM. Mutations in GRIP1 cause Fraser syndrome. J Med Genet. 2012 Apr 17. [Epub ahead of print].

PubMed ID: 
22510445

Aniridia 1

Clinical Characteristics
Ocular Features: 

Aniridia is the name of both a disorder and a group of disorders.  This because aniridia is both an isolated ocular disease and a feature of several malformation syndromes.  Absence of the iris was first reported in the early 19th century.  The hallmark of the disease is bilateral iris hypoplasia which may consist of minimal loss of iris tissue with simple radial clefts, colobomas, pseudopolycoria, and correctopia, to nearly complete absence.  Goniosocopy may be required to visualize tags of iris root when no iris is visible externally.  Glaucoma is frequently present (~67%) and often difficult to treat.  It is responsible for blindness in a significant number of patients.  About 15% of patients are diagnosed with glaucoma in each decade of life but this rises to 35% among individuals 40-49 years of age.  Hypoplasia and dysplasia of the fovea are likely responsible for the poor vision in many individuals.  Nystagmus is frequently present.  The ciliary body may also be hypoplastic. 

Visual acuity varies widely.  In many families it is less than 20/60 in all members and the majority have less than 20/200.  Photophobia can be incapacitating.  Posterior segment OCT changes suggest that outer retinal damage suggestive of a phototoxic retinopathy may also be a factor in the reduced acuity.  Cataracts (congenital in >75%), ectopia lentis (bilateral in >26%), optic nerve hypoplasia, variable degrees of corneal clouding with or without a vascularized pannus, and dysgenesis of the anterior chamber angle are frequently present. 

Increased corneal thickness (>600 microns) has been found in some series and should be considered when IOP measurements are made.  In early stages of the disease, focal opacities are present in the basal epithelium, associated with sub-basal nerves.  Dendritic cells can infiltrate the central epithelium and normal limbal palisade architecture is absent.  The tear film is often unstable.

Systemic Features: 

In addition to 'pure' aniridia in which no systemic features are found, at least six disorders have been reported in which systemic anomalies do occur.  Three of these have associated renal anomalies, including Wilms tumor with other genitourinary anomalies and mental retardation, sometimes called WAGR (194072) syndrome, another (612469) with similar features plus obesity sometime called WAGRO (612469) syndrome reported in isolated patients, and yet another with partial aniridia (206750) and unilateral renal agenesis and psychomotor retardation reported in a single family.  Aniridia with dysplastic or absent patella (106220) has been reported in a single three generation family.  Cerebellar ataxia and mental retardation with motor deficits (Gillespie syndrome; 206700) have been found in other families with anirdia.  Another 3 generation family has been reported in which aniridia, microcornea and spontaneously resorbed cataracts occured (106230).

About one-third of patients with aniridia also have Wilms tumor and many have some cognitive deficits.

Genetics

The majority of cases have a mutation in the paired box gene (PAX6) complex, or at least include this locus when chromosomal aberrations such as deletions are present in the region (11p13).  This complex (containing at least 9 genes) is multifunctional and important to the tissue regulation of numerous developmental genes.   PAX6 mutations, encoding a highly conserved transcription regulator, generally cause hypoplasia of the iris and foveal hypoplasia but are also important in CNS development.  It has been suggested that PAX6 gene dysfunction may be the only gene defect associated with aniridia.  More than 300 specific mutations, most causing premature truncation of the polypeptide, have been identified.  

AN1 results from mutations in the PAX6 gene.  Two additional forms of aniridia have been reported in which functional alterations in genes that modulate the expression of PAX6 are responsible: AN2 (617141) with mutations in ELP4 and AN3 (617142) with mutations in TRIM44.  Both ELP4 and TRIM44 are regulators of the PAX6 transcription gene.

Associated abnormalities may be due to a second mutation in the WT1 gene in WAGR (194072) syndrome, a deletion syndrome involving both WT1 and PAX6 genes at 11p13.  The WAGRO syndrome (612469) is caused by a contiguous deletion in chromosome 11 (11p12-p13) involving three genes: WT1, PAX6, and BDNF.  All types are likely inherited as autosomal dominant disorders although nearly one-third of cases occur sporadically.

Mutations in PAX6 associated with aniridia can cause other anterior chamber malformations such as Peters anomaly (604229).

Gillespie syndrome (206700 ) is an allelic disorder with neurological abnormalities including cerebellar ataxia and mental retardation.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Treatment is directed at the associated threats to vision such as glaucoma, corneal opacities, and cataracts.  Glaucoma is the most serious threat and is the most difficult to treat. The best results have been reported with glaucoma drainage devices.  All patients should have eye examinations at appropriate intervals throughout life, focused on glaucoma screening.  It is well to keep in mind that foveal maldevelopment often precludes significant improvement in acuity and heroic measures must be carefully evaluated.  Specifically, corneal transplants and glaucoma control measures frequently fail.

Low vision aids are often helpful.  Tinted lenses can minimize photophobia.  Occupational and vocational training should be considered for older individuals.

Young children with aniridia should have periodic examinations with renal imaging as recommended by a urologist.

In mice, postnatal topical ocular application of ataluren-based eyedrop formulations can reverse malformations caused by PAX6 mutations.

References
Article Title: 

Familial aniridia with preserved

Elsas FJ, Maumenee IH, Kenyon KR, Yoder F. Familial aniridia with preserved ocular function. Am J Ophthalmol. 1977 May;83(5):718-24.

PubMed ID: 
868970
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